Fluid pressure-operated device

ABSTRACT

A fluid pressure-operated device comprises a piston slidably disposed in a cylinder, pump means for feeding a pressure fluid to the cylinder thereby axially moving the piston against the biasing force of a spring, and return valve means for allowing, when the piston has been moved by prescribed stroke, the pressure fluid within the cylinder to escape therethrough so as to return the piston to the original position.

United States Patent Ishihara Nov. 25, 1975 1 FLUID PRESSURE-OPERATEDDEVICE 2,618,929 11/1952 Bidin .1 60/478 9,4 [76'] Inventor: MasamitsuIshihara, 628 Hirai, 53 ,1 32??? D I Kannami-cho, Tagata, Shiluoka,3,873,844 3/1975 Willis 60/477 Japan [22] Filed: Dec. 13, 1974 App].No.: 532,386

UNITED STATES PATENTS Riach v.91/401 X Primary ExaminerEdgar W.Georghegan [57] ABSTRACT A fluid pressure-operated device comprises apiston slidably disposed in a cylinder, pump means for feeding apressure fluid to the cylinder thereby axially moving the piston againstthe biasing force of a spring. and return valve means for allowing, whenthe piston has been moved by prescribedstroke. the pressure fluid withinthe cylinder to escape therethrough so as to return the piston to theoriginal position.

11 Claims, 6 Drawing Figures US. Patent Nov. 25, 1975 Sheet10f23,921,399

US. Patent Nov. 25, 1975 Sheet20f2 3,921,399

FLUID PRESSURE-OPERATED DEVICE This invention relates to a fluidpressure-operated device, and more particularly to a fluidpressure-operated device for use with a machine tool, though not limitedthereto, by which the reinforcing steel piece shearing or metal platepuncturing as in the case of, for example, the building operations isperformed.

conventionally, the reinforcing steel piece shearing or metal platepuncturing was conducted utilizing an extremely large-sized machine ormanually operable machine tool. This type of machine or machine tool,however, had the drawback of reducing the operation efficiency orrequiring much labour.

Accordingly, the object of the invention is to provide a compact fluidpressure-operated device whose operation is capable of being stabilizedand which is capable of achieving a high operation efficiency.

A fluid pressure-operated device according to the invention comprises apiston slidably disposed in a cylinder and partitioning the cylinderinto two parts, i.e., a low pressure chamber and a high pressurechamber, pump means for feeding a pressure fluid to the high pressurechamber thereby moving the piston toward the low pressure chamberagainst the biasing force of a first spring, and return valve means forallowing, when the piston has been moved toward the low pressure chamberby a prescribed stroke, the pressure fluid within the high pressurechamber to escape therethrough into the low pressure chamber so as toreturn the piston to the original position. Said valve means comprises afirst passageway formed through the piston for allowing the low pressurechamber to communicate with the high pressure chamber, a rod slidablyextending through the piston and protruded at one end into the lowpressure chamber, and a closing member provided within the high pressurechamber on the other end of the rod in a manner integral therewith toclose said passageway due to the action of the fluid pressure of thehigh pressure chamber. When the piston is moved toward the low pressurechamber by the pump means, the valve means is moved together with thepiston in a state closing said passageway. When the piston has beenmoved by a prescribed stroke, said one end is allowed to abut againstfirst stop means to release the closing member to open the passageway,thereby causing the pressure fluid within the high pressure chamber toflow into the low pressure chamber. For this reason, the piston isreturned to the original position by said first spring to cause theclosing member to abut against second stop means, thereby closing againsaid passageway. Thereafter, the piston commences to be again movedtoward the low pressure chamber.

Said one end of the rod may preferably hold a floating compressionspring. When the piston has been moved by a prescribed stroke, thecompression spring is sufficiently compressed by the first stop meansand subsequently, when the passageway has been opened, acts to rapidlypush the rod toward the high pressure chamber.

The piston may be provided with a piston rod extending through the lowpressure chamber to be protruded to the exterior and a machine tool onthe tip end of the rod. The machine tool is forwardly advanced inaccordance with the movement of the piston to machine the objectworkpiece. In this case, the low pressure chamber can preferably beprovided with compensation 2 means for compensating an increase ordecrease in the chamber volume produced due to the reciprocatingmovement of the piston in the low pressure chamber.

In a preferred embodiment of the invention, there is provided safetyvalve means for allowing, when an accident has occurred, a pressurefluid within the high pressure chamber to escape therethrough into a lowpressure chamber. Said valve means consist of a normally closed valveprovided in a second passageway for con necting the high pressurechamber with the low pressure chamber.

This invention will now be described in more detail by reference to theappended drawings in which:

FIG. 1 is a longitudinal sectional view illustrating a fluidpressure-operated device according to the inven' tion;

FIG. 2 is an enlarged view illustrating part of the fluidpressure-operated device, wherein the piston is in a position moved by amaximum stroke;

FIG. 3 is a perspective view illustrating another embodiment of thereturn valve means;

FIG. 4 is an enlarged plan view, partly in section, of the devicesection on which a machine tool is mounted; and

FIGS. 5 and 6 respectively are enlarged views illustrating amodification of the compensation means.

In FIG. 1, a fluid pressure-operated device of the invention applied toa shearing machine 10 for reinforcing steel is illustrated. The shearingmachine 10 comprises a housing 11 for receiving therein a fluidpressure-operated mechanism and a known internal combustion engine 13fixed to the housing. The internal combustion engine acts as a powersource for driving the fluid pressure-operated mechanism and comprises astarter 14, ignition plug 15 and fuel tank 16. The engine 13 may bereplaced by an appropriate power source such as, for example, anelectric motor. Reference numerals and 81 respectively denote a handlefor holding the shearing machine in place.

A reservoir 17 fluid-tightly shut off from the exterior and filled withan operating fluid is defined by the inner wall of the housing 11. Aport 82 provided in the bottom portion of the reservoir is used topermit the fluid to be introduced therethrough or exhausted therethroughinto or from the reservoir, and is normally closed by a plug 83. Thereservoir is divided by a partition wall 18 into two parts, i.e.,reservoir sections and 17b, which communicate with each other through apassageway 19. The partition wall 18 defines a cylinder with thecylindrical inner wall portion 20 of the housing 11. Within the cylindera later described diskshaped piston 21 is slidably and fluid-tightlydisposed via a seal ring 22 to form a high pressure chamber 23.

On the right end portion of the housing 11 is rotatably mounted via ballbearings 24 and 25 a shaft 26, the right end of which is connected via aknown centrifugal clutch 27 to the engine 13. The clutch consists of aclutch drum 28 fixed to the right end of the shaft and a clutch expander29 mounted on the drive shaft (not shown) of the engine. When therotation speed of the engine has increased up to a value larger thanprescribed, the expander is frictionally engaged with the drum 28 totransmit a driving force to the shaft 26.

The left end of the shaft 26 is fluid-tightly inserted into thereservoir 17 via a seal ring 30, and is provided with a pump 31 ofradial plunger type. The pump comprises a cam rod 32 eccentrically fixedto the shaft 26, a needle roller bearing 33 provided on the cam rod, and

a plurality of radial plungers 34 (only one of which is illustrated)equi-angularly arranged on the circumference of the bearing 33. Eachplunger is slidably disposed in each of a plurality of radiallyextending cylindrical bores 35 formed in the inner wall of the housing11, and is urged against the outer ring of the bearing 33 by the biasingforce of a spring 36. The cylindrical bore 35 communicates with thereservoir 17 via a passageway 37 and with the high pressure chamber 23via a one-way valve 38 and a passageway 39. When the plunger 34 makes areciprocating movement in accordance with the eccentrical rotation ofthe cam rod 32, a fluid within the reservoir 17 is fed under pressure tothe high pressure chamber 23 via the passageway 37, bore 35, valve 38and passageway 39.

The above-mentioned piston 21 is always urged toward the right side ofFIG. 1 by the biasing force of a compression spring 40, and, when theforce of pressure fluid from the pump 31 has become superior to thebiasing force of said spring, is moved toward the left side of FIG. 1.

Referring to FIGS. 1 and 2, the piston 21 is provided with return valvemeans 41 for allowing, when the piston has been moved toward the highpressure chamber by a prescribed stroke, the pressure fluid within thehigh pressure chamber23 to escape therethrough into a low pressurechamber, i.e., reservoir section 17b. The return valve means comprises avalve rod 43 fluidtightly and slidably inserted into a hole 42 extendingthrough the piston. The piston wall on the high pressure chamber side isformed with a circular recess 44 concentrical to the valve rod 43, saidrecess communicating with the reservoir section 17b through a pressurefluid escapement passageway 45 formed through the piston. The valve rodhas a disk-shaped closing head 46 at its end portion on the highpressure chamber side, and the edge portion 47 of said head is designedto shut off, when engaging the wall of the piston 21, communication ofthe chamber 23 with the recess 44. The left end of the valve rod 43 isallowed to projectively extend into the reservoir section 17b and holdsa com pression spring or kick spring 48. The spring 48 is fixed at oneend to the left end of the rod 43 and projectively extends from the leftend of the rod with the other end thereof rendered free. The inner wallportion 49 of the housing facing the left end of the rod 43 constitutesa stop for the rod 43 and the spring 48, and the maximum intervalbetween the portion 49 and the left end of the rod 43 corresponds to themaximum stroke of the piston 21.

When a pressure fluid is fed from the pump 31 to the high pressurechamber 23 with the passageway 45 closed by the closing head 46, thepiston 21 commences to be moved leftward against the compression spring.At this time, the closing head 46 is moved jointly with the piston 21 ina state closing the passageway 45 by the high fluid pressure in the highpressure chamber 23. When the piston has been moved by a prescribedstroke, the kick spring 48 first abuts against the stop 49 and then isgradually compressed. When the piston has been further moved, the leftend of the valve rod 43 abuts against the stop 49, thereby causing theedge portion 47 of the closing head 46 to be released from the wall ofthe piston 21. For this reason, the high pressure fluid within the highpressure chamber 23 is enabled to escape into the reservoir section 17b,i.e., low pressure chamber through the interspace between the edgeportion 47 and the wall 'of the piston 21,

thereby reducing the internal pressure of the chamber 23 andsimultaneously causing the kick spring 48 to forcibly push the valve rod43 toward the right by its accumulated force. When, at this time, therotation speed of the engine is decreased and the clutch 27 is released,the pressure fluid within the chamber 23 quickly escapes through thepressure fluid escapement passageway 45 into the reservoir section 17b.Therefore, the piston 21 is returned to the position of FIG. 1 by thebiasing force of the compression spring 40. The closing head 46 abutsagainst the partition wall 18 to close the passageway 45 again, and whena pressure fluid is sent from the pump 31, the same process beginsagain. A compression spring 50 disposed between the bottom portion ofthe recess 44 and the head 46 so acts as to apply to the head 46 aweaker force than the high pressure within the high pressure chamber,and serves as means for maintaining the head spaced from the piston wallduring the return stroke of the piston 21.

In an embodiment illustrated in FIG. 3, a piston 21a is provided withtwo return valve means 410 positioned radially of the piston 21a in amanner mutually opposite each other with the piston center interveningtherebetween. The respective valve means 41a have a constructionsubstantially the same as the return valve means 41 illustrated in FIGS.1 and 2 except that their head 46a has a shock absorber 75. In thiscase, when one valve means 41a is opened, the other valve means is alsoopened at once due to reduction in the internal pressure of the highpressure chamber. For this reason, the valve means can be constructed torelatively small size measurements. Further, since the pressure fluidwithin the high pressure chamber is flowed through both said valvemeans, the piston 21a can be returned to the original position in awell-balanced state.

From the piston 21 there coaxially extends a rod 51, which isfluid-tightly and slidably inserted via a seal ring 53 into acylindrical bore 52 formed in the housing 11. The outer wall of the rod51 is formed with a key way 54 extending in the longitudinal direction.To the inner wall of the bore 52, as shown in FIG. 4, is fixed via abolt 56 a key 55, which engages thekey way. To the tip end of the rod 51is secured a cutter 57, which is so designed as to cooperate with acutter 58 secured to the housing 11. An unsheared workpiece such as, forexample, a reinforcing steel piece is placed between the cutters 57 and58, and subsequently when the cutter rod 51 is moved jointly with thepiston 21 to the left of FIG. 1, said reinforcing steel piece is cut offby the cutters 57 and 58.

In this type of shearing machine, where the unsheared workpiece is toohard to permit the rod 51 to be forwardly advanced, the piston 21 shouldbe backwardly returned halfway. To this end, the housing 11 is formedwith another passageway 59 for allowing the high pressure chamber 23 tocommunicate with the reservoir section 17b. Within the passageway 59 isdis posed a ball valve 60, which is normally pressed by a threaded stem61 screwed into the housing 11 to shut the passageway 59 off. In thecase of accident occurrence, when the operator slows down the rotationspeed of the engine and swings the lever 62 secured to the outer end ofthe stem 61, the passageway 59 is opened to allow the pressure fluidwithin the high pressure chamber 23 to escape into the reservoir section17a. For this reason, the piston 21 is returned to permit piece.

The shearing machine according to this embodiment is provided with meansfor compensating an increase or decrease in the reservoir volume due tofluid leakage or reciprocating movement of the piston. In the embodimentillustrated in FIG. 1, the compensation means comprises a flexible bag63 made of a material such as rubber or plastic and disposed within thereservoir section 17b. The bag is fixed to a bolt 66 having a throughhole 65. The bolt 66 is fitted by screw engagement into a threaded hole67 formed in the housing and fixed by a nut 68. The head 66a of the boltfluid-tightly presses the edge of the bag 63 against the inner wall ofthe reservoir. The bag 63 is expanded or shrunk in accordance with fluidleakage or reciprocating movement of the rod 51, thereby preventingentry of air into the reser- VOlr.

In an embodiment illustrated in FIG. 5 the reservoir section 17bincludes a cylindrical hole 69 which communicates with the exteriorthrough an air hole 70. Said compensation means comprises a pistonmember 72 fluid-tightly and slidably disposed in the cylindrical hole 69via an O-ring 71. The piston member is always lightly urged toward theright of the illustration by the biasing force of a compression spring73 and makes a sliding movement in accordance with the volume variationof the reservoir, or with the fluid leakage.

Compensation means illustrated in FIG. 6 comprises a piston member 75having a flexible bag 74. This piston member is slidably disposed in acylindrical hole 690. The interior of said bag 74 communicates with theopen air through a hole 76 formed through the piston member and an airhole 700. In the case of this embodiment, the volume variation of thereservoir is compensated principally by expansion or shrinkage of thebag 74, while the fluid leakage is compensated principally by thesliding movement of the piston member 75.

In the compensation means illustrated in FIGS. 5 and 6, a filteringmember may be provided in the air hole 70 or 70a for the purpose ofpreventing entry of dust into the cylindrical hole.

The foregoing description referred to the case with the shearingmachine, but the fluid pressure-operated device of the invention canalso be applied to a puncturing machine, calker, or the like. In suchcases a puncturing machine tool or calking machine tool in replacementof said cutters may be mounted on the piston rod.

What is claimed is:

1. A fluid pressure-operated device comprising a cylinder, a pistonslidably disposed in said cylinder and partitioning said cylinder intotwo parts one of which is a low pressure chamber and the other of whichis a high pressure chamber, a first spring for urging said piston towardthe high pressure chamber, pump means for feeding a pressure fluid tothe high pressure chamber, thereby moving the piston toward the lowpressure chamber against the biasing force of said first spring, and atleast one return valve means for allowing, when the piston has beenmoved toward the low pressure chamber by a prescribed stroke, thepressure fluid within the high pressure chamber to escape therethroughinto the low pressure chamber so as to return the piston to the highpressure chamber, said return valve means including a rod elementaxially and movably extending through the piston and having one endprotruded into the high pressure chamber and the other end protrudedinto the low pressure chamber, a first passageway formed through thepiston and allowing the high pressure chamber to communicate with thelow pressure chamber, a closing element integrally provided on said oneend of the rod element to close the first passageway due to the actionof the fluid pressure in the high pressure chamber, and a stop againstwhich; when the piston has been moved by a prescribed stroke, said otherend abuts to permit the closing ele' ment to open the first passageway.

2. A fluid pressure-operated device according to claim 1 wherein saidreturn valve means includes a second compression spring held by saidother end of the rod element and projectively extending therefrom.

3. A fluid pressure-operated device according to claim 2 wherein saidreturn valve means includes a third compression spring for maintainingthe closing element in a state spaced from the first paassageway duringthe return stroke of the piston.

4. A fluid pressure-operated device according to claim 1 furthercomprising a second passageway allowing the high pressure chamber tocommunicate with the low pressure chamber and a safety valve fornormally closing said second passageway.

5. A fluid pressure-operated device according to claim 4 wherein saidsafety valve includes a manually operable lever for opening the same.

6. A fluid pressure-operated device according to claim 1 wherein saidpiston includes a piston rod extending through the low pressure chamberto be protruded exteriorly thereof and a machine tool mounted on theouter end of said piston rod.

7. A fluid pressure-operated device according to claim 6 furthercomprising a reservoir communicating with the low pressure chamber, forholding therein the fluid for the pump, said reservoir havingcompensation means for compensating the volume variation of thereservoir resulting from the reciprocating movement of said piston rod.

8. A fluid pressure-operated device according to claim 7 wherein saidcompensation means consists of a flexible bag provided within thereservoir, the interior of said bag communicating with the open air.

9. A fluid pressure-operated device according to claim 7 wherein saidreservoir includes a cylindrical section communicating at one end withthe open air, and said compensation means includes a second pistonslidably and fluid-tightly disposed in said cylindrical section.

10. A fluid pressure-operated device according to claim 7 wherein saidreservoir includes a cylindrical section communicating at one end withthe open air, and said compensation means includes a second pistonslidably and fluid-tightly disposed in said cylindrical section andhaving a through hole formed therethrough and a flexible bag fixed tosaid second piston at the res ervoir side and communicating interiorlywith the open air via said through hole.

11. A fluid pressure-operated device according to claim 1 wherein saidpump means is a radial plunger type.

1. A fluid pressure-operated device comprising a cylinder, a pistonslidably disposed in said cylinder and partitioning said cylinder intotwo parts one of which is a low pressure chamber and the other of whichis a high pressure chamber, a first spring for urging said piston towardthe high pressure chamber, pump means for feeding a pressure fluid tothe high pressure chamber, thereby moving the piston toward the lowpressure chamber against the biasing force of said first spring, and atleast one return valve means for allowing, when the piston has beenmoved toward the low pressure chamber by a prescribed stroke, thepressure fluid within the high pressure chamber to escape therethroughinto the low pressure chamber so as to return the piston to the highpressure chamber, said return valve means including a rod elementaxially and movably extending through the piston and having one endprotruded into the high pressure chamber and the other end protrudedinto the low pressure chamber, a first passageway formed through thepiston and allowing the high pressure chamber to communicate with thelow pressure chamber, a closing element integrally provided on said oneend of the rod element to close the first passageway due to the actionof the fluid pressure in the high pressure chamber, and a stop againstwhich, when the piston has been moved by a prescribed stroke, said otherend abuts to permit the closing element to open the first passageway. 2.A fluid pressure-operated device according to claim 1 wherein saidreturn valve means includes a second compression spring held by saidother end of the rod element and projectively extending therefrom.
 3. Afluid pressure-operated device according to claim 2 wherein said returnvalve means includes a third compression spring for maintaining theclosing element in a state spaced from the first paassageway during thereturn stroke of the piston.
 4. A fluid pressure-operated deviceaccording to claim 1 further comprising a second passageway allowing thehigh pressure chamber to communicate with the low pressure chamber and asafety valve for normally closing said second passageway.
 5. A fluidpressure-operated device according to claim 4 wherein said safety valveincludes a manually operable lever for opening the same.
 6. A fluidpressure-operated device according to claim 1 wherein said pistonincludes a piston rod extendiNg through the low pressure chamber to beprotruded exteriorly thereof and a machine tool mounted on the outer endof said piston rod.
 7. A fluid pressure-operated device according toclaim 6 further comprising a reservoir communicating with the lowpressure chamber, for holding therein the fluid for the pump, saidreservoir having compensation means for compensating the volumevariation of the reservoir resulting from the reciprocating movement ofsaid piston rod.
 8. A fluid pressure-operated device according to claim7 wherein said compensation means consists of a flexible bag providedwithin the reservoir, the interior of said bag communicating with theopen air.
 9. A fluid pressure-operated device according to claim 7wherein said reservoir includes a cylindrical section communicating atone end with the open air, and said compensation means includes a secondpiston slidably and fluid-tightly disposed in said cylindrical section.10. A fluid pressure-operated device according to claim 7 wherein saidreservoir includes a cylindrical section communicating at one end withthe open air, and said compensation means includes a second pistonslidably and fluid-tightly disposed in said cylindrical section andhaving a through hole formed therethrough and a flexible bag fixed tosaid second piston at the reservoir side and communicating interiorlywith the open air via said through hole.
 11. A fluid pressure-operateddevice according to claim 1 wherein said pump means is a radial plungertype.